What is our aim in liturgy? No less than union with God. This is accomplished not only in the Eucharist, but also in the entire liturgical life of the Church:
138. The ideal of Christian life is that each one be united to God in the closest and most intimate manner. For this reason, the worship that the Church renders to God, and which is based especially on the eucharistic sacrifice and the use of the sacraments, is directed and arranged in such a way that it embraces by means of the divine office, the hours of the day, the weeks and the whole cycle of the year, and reaches all the aspects and phases of human life.
139. Since the divine Master commanded “that we ought always to pray and not to faint,”[Luke 18:1] the Church faithfully fulfills this injunction and never ceases to pray: she urges us in the words of the Apostle of the Gentiles, “by him Jesus let us offer the sacrifice of praise always to God “[Heb. 13:15]
And so we begin a long look at the Liturgy of the Hours in Mediator Dei, sections 138-150. Remember, this document is addressed to bishops, so these next several sections would have been of greater interest to the episcopacy, parish priests, and those in religious orders.